Multi-homed box acting as a DNS and Mail Server.

Barry Margolin barmar at genuity.net
Tue Apr 11 18:56:49 UTC 2000


In article <38F370DB.FAB1F82E at home.com>, Melvin Toy  <mwtoy at home.com> wrote:
>I'm a newbie experimenting with bind and sundial.  I have a box at home
>with 2 nics(one real static IP and other private 172.16.x.x) running
>Redhat 6.1 with a cable modem.  I have another box (box A) running RH6.1
>at home with a private IP and one (box B) at work running solaris 2.7
>with a real IP. I temporary add my DNS server as the name server for box
>B. I can email from my dns/mail server and it also relays box A messages
>to box B and masquerades correctly.  However when I reply, my mail
>bounces.  I tried to telnet to port 25 by FQDN of the dns/mail server
>from box b.  I notice it was trying to telnet to the private IP instead
>of the real one.  When I do an nslookup by name both IPs are return.
>How do I get box B to use the real IP every time.  I know I going to
>have more issues with sendmail but I'm trying to eliminate all
>non-sendmail problems first. My first thought is to create a separate
>record for the internal nic. Is that legitimate and typical solution?
>How will that will affect sendmail?

Creating separate names for the two NICs is probably the simplest
solution.  I don't think it should affect sendmail at all.

The more complicated solution is to run multiple instances of BIND on the
server.  They would each have their own named.conf file and zone files.
Use the listen-on option in named.conf to make each one bind to the address
of a different NIC, and put the appropriate address in the corresponding
zone file.

Another solution is to use the sortlist directive in the client machines'
/etc/resolv.conf files to make them sort the address on their network
first.

-- 
Barry Margolin, barmar at genuity.net
Genuity, Burlington, MA
*** DON'T SEND TECHNICAL QUESTIONS DIRECTLY TO ME, post them to newsgroups.
Please DON'T copy followups to me -- I'll assume it wasn't posted to the group.



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